September 28, 2014

I’ve always been kind of partial to spiders, though at the same time just a bit intimidated by them.  Although the vast majority of North American spiders are of no significant threat to people, the idea of catching a big orb-weaver in the face when I’m in the field still creeps me out if I think about it.  My real introduction to spider biology at anything other than an extremely superficial level came when I first began grad school at UF, and became friends with an arachnophile, Craig Hieber.  Much of what I know about Florida spiders I learned from Craig, and though I can’t say for certain that he was the one who first introduced me to the green lynx spider, I think there’s a pretty good chance he did.  UF Zoology at that time was a hotbed of spider research – faculty members John Reiskind and John Anderson both did research on spiders, and mentored a number of grad students doing their master’s or doctoral research.  Even H. Jane Brockmann, always one of my favorites among the faculty (“do you people say bloody over here?”), got in on the spider action, and her student Linda Fink produced some splendid papers on reproduction and defense by green lynx spiders as an outcome of her master’s thesis.

Green lynx spiders, Peucetia viridans, are one of the most common Florida spider species.  They prompt the greatest number of requests for identification by the arthropod experts at the Florida State Collection of Arthropods of any spider species in Florida.  Commonly found in ruderal (disturbed) habitats and edges, particularly among flowers in the late summer and fall, I’ve known about their abundance for some time.  When I first moved to my current home in DeLand six years ago, the gardens I planted were loaded with lynxes.  More recently, since I’ve begun spending a lot of my field time ode-cruising, I’ve been struck again how incredibly common they are.   Green lynxes can be pretty cryptic as they spend large amounts of time motionless amidst an inflorescence waiting for some clueless victim to make the mistake of a lifetime, but once you’ve developed a search image, you can’t help noticing them.

They are so abundant in some habitats, including agricultural fields, that they are an effective biological control agent against some agricultural pests, particularly the many species of noctuid moths that oviposit and feed as larvae on crop plants.  The good that lynxes do by reducing herbivory on crop plants is counteracted somewhat by the number of beneficial insects they consume along with the pests.  Bees, wasps, butterflies and skippers, syrphids and other types of flies… the list goes on and on. Lynx spiders seem to be very opportunistic predators who will take just about any type of insect prey that they can get their fangs on.

 

And what lovely fangs (chelicerae) they have.  Members of the family containing the lynxes, the Oxyopidae, are distinguished by their relatively tall clypeum (the portion of the “face” between the eyes and the chelicerae) and elongate chelicerae.  Looking at a lynx spider head-on makes me think of an old, droopy-faced wizard.  The Oxyopidae is not a huge family – a bit over 400 species in 19 genera worldwide, in Florida they are represented by only a few species in two genera (Peucetia and Oxyopes).  I’ve never seen any of the Oxyopes species, but I’ve seen more lynxes than you can shake a snake hook at.  They are ubiquitous at this time of year.

Finding them isn’t hard.  I’ve seen them referred to in one source as “Inflorescence spiders”, and that is spot on.  If you want to find lynxes, look for them on the inflorescences of a variety of weedy plants, including many composites.   Because they are so cryptic, it helps to look for particular irregularities in flower clusters, like an out-of-place green lump in the midst of the flowers, or the translucent spiny legs projecting out from the flowers.  I’ve lost count of the number of times I’ve found lynx spiders lurking in the background when doing post-processing of photos of other flower visitors.  With their delicate green cephalothorax and abdomen, decorated by whitish chevrons in the larger females, and their nearly transparent multicolored spiny legs, there is nothing to confuse a lynx spider with.  

Though I’ve been seeing and appreciating lynxes for years, I was thrilled to recently photograph a male lynx for the first time. Males are slightly smaller than females, but as in most spiders, males are distinguishable from females by their modified pedipalps.  Pedipalps, or palps for short, are the pair of short leg-like appendages extending from the head, with which spiders manipulate  prey or other objects.  Palps are also intimately involved in mating behavior – they are the surrogate penises for males.   Prior to mating, male spiders spin a pad of silk and deposit semen on it and transfer the sperm to receptacles at the end of their palps.  Male spider palps are typically enlarged at the end, sometimes with syringe-like structures and extensions that aid in the process of inseminating the female.  I wonder if female spiders reluctant to mate sometimes give “palp jobs” to persistent males to cool them down?

Lynx spiders obtain their name from their hunting behavior.  They are ambushers and stalkers, using their acute vision to track and pounce on unwary prey.   I’ve never been lucky enough to see one making a kill, but I have on several occasions watched a hunting lynx make a quick dart towards pollinators approaching the flower they are sitting on.   Just yesterday I photographed one that had just seconds previously captured a small darkly-colored grass skipper; the lynx had her fangs embedded in the skipper, and it slowly unfurled and then recoiled it’s proboscis as the venom took hold.  At one point the struggling skipper forced the lynx to release her hold on the plant, and the spider and her skipper prey dangled from a few silk lines, spinning in the faint breeze until she regained her purchase.

Did someone say badass?  Lynx spiders seemingly know no fear.  They’ll take just about any prey they can inject their venom into, including some insects as large or larger than the spider.  Occasionally, however, the tables are turned and insects that could be taken as prey take the spider.  Many species of solitary wasps provision their nests with paralyzed spiders to feed their developing offspring, and lynx spiders are among the victims.

On a number of occasions, I’ve seen lynx spiders with prey being victimized by another arthropod colleague, though not with such drastic results as their interactions with spider wasps.   Lynx prey items are sometimes attacked by hemolymph-sucking ceratopogonid flies (midges) as the spider is sucking out the liquefied prey contents.   I don’t know whether the midges also attack the lynx, but they do parasitize other adult arthropods, such as dragonflies.

 Aside from their general ferociousness and take-no-prisoners attitude, lynx spiders show a gentle side.  They are excellent mothers.  Linda Fink’s research while at the University of Florida revealed that females guard their egg cases (cocoons) for several weeks after they lay the eggs, and that this defensive behavior significantly increases survivorship of cocoons when compared to experimentally manipulated cocoons from which the female had been removed.  Ants seem to be the biggest threat; the female lynx will directly attack the ants, though on occasion they will chomp down on a leg and not release their grip even after death.  Linda observed lynx spiders in some instances sacrificing a leg (autotomy) to rid themselves of the dead hanger-on.   Their maternal devotion doesn’t protect the eggs from one other threat, though – parasitic mantidflies (Mantispidae) that lay their eggs in the spiders’ cocoons were equally common in both Linda’s control (mother remained) and experimental (mother removed) treatments.

Linda even documented a new defensive behavior for lynxes while doing her research on maternal care – they spit venom in the direction of their enemy.   Although there is an entire family of spiders that specializes on spitting their gooey silk-containing venom cocktail on their prey to immobilize them (the Scytodidae), green lynx spiders are the only oxyopids known to defend themselves in this way.

If the standard defensive measures don’t work, lynx mothers will relocate their cocoon to another plant.  But they do so in a unique way; they don’t carry the cocoon to its new site, as some other spiders do, but instead reengineer its attachment.   They establish new suspensory silk lines anchoring the cocoon to the foliage of a nearby plant, and then cut the silk lines attaching it to its current host.  The cocoon swings over to its new site and the female then secures it with more silk. 

She stays with the developing eggs in the cocoon for several weeks until they hatch, sometimes refraining from feeding and starving herself in the process.  The cocoon can contain 25-600 eggs, averaging about 200.  Whether the female refrains from feeding or not, she will die sometime during the fall, and her early-instar offspring will overwinter, maturing and reproducing themselves about 300 days later. 

My next photographic goal – obtain a cocoon or two, with attending female, and keep them in captivity until the little dudes hatch.  Is there anything more adorable than a batch of a couple hundred little lynx spiderlings being doted on by a loving mother?  I doubt it.

References

Fink, L.S. 1986.  Costs and benefits of maternal behaviour in the green lynx spider (Oxyopidae, Peucetia viridans).  Animal Behaviour 34(4):  1051-1060.

Fink, L.S. 1987.  Green Lynx Spider Egg Sacs: Sources of Mortality and the Function of Female Guarding (Araneae, Oxyopidae).  Journal of Arachnology 15(2): 231-239.

 

 

September 20, 2014

I’m undergoing a seismic shift in my natural historizing, it seems.  Normally this time of year I’d be out in the field on any morning I can, frantically seeking migrant songbirds (and often failing).  Thus far this migration season, which began back in early August for me, I’ve spent virtually no time seriously birding.  I’ve been out several mornings with birds in mind, but when avian action was not readily forthcoming, I switched my focus to a more attainable target – insects and other spineless beasts.  Two reasons: I could find them, and I could photograph them.

I have this bizarre compulsion that taints everything I do when digging on the natural world – I have to take photographs of whatever I’m seeing, if at all possible.  It’s an affliction really, that impacts my ability to just chill the fuck out and groove on nature.   Close friends who come to visit me and sit on my porch and watch birds with me have remarked on this on numerous occasions.  Do you really need more photographs of northern cardinals?  Point taken.

Nonetheless, as some great sage (who I may be related to) once said, it is what it is.  One of the many benefits of teaching college is the extended vacations, which allow me to devote most of my energies to some goal I find hard to accomplish during the semester.  This past summer, my main goals were to increase my fluency in field botany and to learn to find, identify, and photograph dragonflies and damselflies, the odes of the title (a bug geek term for insects in the order Odonata).   In pursuit of odes, I’ve rediscovered my fascination with hexapods of all sorts; insects are so unendingly diverse and intriguing that one could spend a lifetime studying the natural history of insects in Volusia County and still only scratch the surface.  On the worst birding days, it’s very rare that you can’t find some interesting arthropods to ponder.

So odes have been a primary focus for me the last several months.  But photographing them requires getting fairly close, if one is using a typical macro lens in the range of 100-200mm focal length.   Plus, I do a lot of observation and photography from the car, which allows me to cover way more habitat than I ever could awheel.  (Is that a word? Afoot, awheel – why not?) Further, dragging my chair out of the backseat and getting self-mobile takes a couple of minutes, so even if the substrate is doable for me, getting out for every photo op just isn’t a workable strategy for me and those of my ilk.  Driving close enough to a perched dragonfly to get a reasonable image with my usual insect lens, a 150mm Sigma macro, is pretty tough to do.   Dragonflies can be pretty wary beasts. For several years I’ve tried sporadically to take “macro” photos of some larger inverts, like odes, with my main bird lens, a 150-500 Sigma.   But at the closest focus distances, I was having a lot of trouble consistently getting sharp images.   Sometimes razor, sometimes vaseline.

My breakthrough with odonate photography from the car came in August, when a female mud dauber began building a nest in the tracks of my sliding glass door, and I decided to try and photograph her.   She was too high for me to get decent shots with my standard macro, and the angle would be too steep if I shot from right underneath her anyway.   I remembered a 20-year old lens I had relegated to the photo gear graveyard soon after I went digital and got the big Sigma zoom.  The old lens was also a Sigma, a 400mm 5.6 lens that was the first refractive lens I used seriously for bird photography.  For a couple of decades I had wasted my time trying to do bird photography with one of the horrid old mirror lenses, which were cheap for their long focal lengths, but generally produced rather low-quality images.   A coincidental meeting at Lake Woodruff NWR with the great bird photographer Artie Morris, who I’d never heard of at the time, enlightened my world.  From a distance, I was blown away by the gigantic camouflaged 600mm lenses and Gitzo tripods he and his companion were toting (big-time big lens envy), so when we passed I chatted them up a bit.  When I showed Artie my mirror lens rig, he graciously avoided snorting in derision, and suggested I upgrade to a refracting 400 f 5.6.  He took a body with his 400 f5.6 Canon lens (his “toy lens”) from around his neck and allowed me to look through it.  I was sold, and bought the Sigma 400 soon after.

I used that lens for years when I did slide photography, and it was a splendid lens.  Incredibly slow 1st-generation autofocus, with no internal motor, but I never used that when I shot with a film body.   But it was renowned for its sharpness, and it was sold as a “Macro” lens.  Not really, but it would focus close enough to get to a 1:3 reproduction ratio, which is pretty decent for a lens with that much reach.  Perfectly suitable for larger insects.  So it occurred to me to drag that old relict out, set it up on a tripod with a soft-boxed flash, and focus on the dauber’s nest, waiting for her regular returns.  I was impressed again by the image quality, and the Sigma 400 became my lens of choice for insect photography from the car.  I doesn’t have any of the vibration reduction systems typical of long telephotos these days, so handholding it and getting critical sharpness are mutually exclusive.  I normally shoot from a beanbag on my car door when doing automotive photography, and that setup is rock solid.

So that’s how I shifted my focus from cruising for birds, which can be abysmally slow in the summer, to cruising for dragonflies, which is usually exactly the opposite.  Ode cruising, I call it.  And in the process, I began keying in on the other big arthropods that can be spotted and photographed while ode cruising.  As it turns out, the most commonly observable and shootable big insects I see are grasshoppers and katydids, of the order Orthoptera.  Orthops for short.

So these days, I get more excited about the idea of photographing orthops and odes more than the prospect of photographing birds.  Both dragons and hoppers are amazingly intricate and photogenic insects, but I’ve been struck repeatedly by my blatant taxonomic bias – I’d far rather find and photograph odes than I would orthops.  Notwithstanding the fact that orthopterans include some of the most striking and beautifully colored insects in the world, and at the other end of the extreme orthops that are exquisitely cryptically colored to blend with their surroundings, an equally astounding feat of adaptation.  Still, for me, dragonflies are the shit.   It’s an incredibly overused metaphor, but I’ll use it anyway – dragonflies are the attack helicopters of the insect world.  I remember seeing Coppola’s opus Apocalypse Now for the first time (and many times thereafter), marveling at the incredible cinematography.  While watching with mouth agape as Colonel Kilgore and the air cavalry attack the point where the waves break in both directions (“Charlie don’t surf!) to drop Willard and his PBR crew into the mouth of the Nung, I remember thinking that the Hueys in slow motion were like nothing so much as giant dragonflies.  The precision and power of odonate flight is awesome, and they are some bad, badass predators.   Seeing one ode munching on another nearly its own size makes me very happy they don’t get any bigger than they do.  Magnificent animals.

On the other hand, orthops are the heavy equipment of the insect world, to me.  Generally slow, lumbering, inoffensive and unaggressive – all fine qualities for an animal, but not as likely to arouse my intense awe as those of rapid and wary predators.  But orthops are charming, colorful and diverse beasts that frequent weedy roadsides, so how could I pass them up?

And every now and then, I see other cool critters, like spiders, and owlflies.  I may be more taken with the spiders than I am with the odes these days.   But that’s another post.

One of the unanticipated benefits of immersing myself into new taxa to explore and photograph is that it delivers a big dose of humility.  It doesn’t take long to realize how little I actually knew about them before, and how much there is in front of me to learn.  And that’s cool.